Stamping die and stamping method

Abstract

The stamping die (21) involved in the present invention forms a stamped part (1), and the stamped part (1) has: a top plate portion (3); a longitudinal wall portion (5), which is continuous with the top plate portion (3) and has a concave portion (7) that is recessed from the edge portion on the opposite side of the top plate portion in side view, that is, the lower edge, toward the top plate portion (3); and a flange portion, which is formed outwardly at the lower edge of the longitudinal wall portion (5). The concave portion (7) successively has, starting from the lower edge (11) of the portion with a greater wall depth: a first bending portion (17), which is continuous with the lower edge; an inclined edge portion (13), which is continuous with the first bending portion (17); a second bending portion (19), which is continuous with the inclined edge portion (13); and a concave edge portion (15) with a shallower wall depth. The flange formed at the first bending portion (17) is a shrink flange, and the flange formed at the second bending portion (19) is an extended flange.

Description

Technical Field

[0001] The present invention relates to a press forming die and a press forming method for press forming automotive parts and other members from a metal sheet, and particularly relates to a press forming die and a press forming method for a press forming part having a top portion, a side wall portion having a portion where the wall height changes when viewed from the side, and a flange portion formed on a side portion opposite to the top portion of the side wall portion, that is, a bottom edge. Background Art

[0002] In recent years, due to the weight reduction of the automotive body caused by environmental problems, high-strength steel sheets are often used for automotive parts. However, compared with steel sheets having low strength, high-strength steel sheets lack elongation and are prone to fracture during processing. In addition, even when high-strength steel sheets are used, in order to further reduce the weight, sheet metal thinning is also carried out at the same time. Therefore, there is also a problem that buckling of the steel sheet is likely to occur and wrinkles are likely to occur during press forming. Therefore, there is a strong demand for the development of a press forming method for suppressing fracture and wrinkles.

[0003] For example, Patent Document 1 discloses a press forming method for manufacturing an automotive part that is prone to wrinkles and stretch flange fractures inside the product without forming defects by using a wrinkle suppression pad that is driven separately from the punch and the die. According to the method disclosed in Patent Document 1, an automotive part that is prone to wrinkles and cracks inside the product can be manufactured without forming defects.

[0004] Patent Document 1: Japanese Patent Publication No. 6032374

[0005] However, the stamping method disclosed in Patent Document 1 is a method that requires using a wrinkle suppression backing plate to restrain the interior of the product away from the flange. Therefore, there is a problem that it cannot be applied to a shape in which wrinkles and cracks are generated in the flange portion itself. Summary of the Invention

[0006] The present invention has been completed in view of the above problems, and an object thereof is to provide a stamping die and a stamping method that can also be applied to a stamping formed part in which wrinkles and cracks are generated in the flange itself and can simultaneously suppress the wrinkles and cracks generated in the flange.

[0007] The stamping die according to the present invention forms a stamped part. The stamped part has: a top plate portion; a longitudinal wall portion that is continuous with the top plate portion and has a recessed portion that is recessed from the edge portion on the opposite side of the top plate portion in a side view, that is, the lower edge, toward the top plate portion side; and a flange portion that is formed outwardly at the lower edge of the longitudinal wall portion. The recessed portion successively has, starting from the lower edge of the portion with a deeper wall depth: a first curved portion that is continuous with the lower edge; an inclined side portion that is continuous with the first curved portion; a second curved portion that is continuous with the inclined side portion; and a recessed side portion with a shallow wall depth. The flange portion formed at the first curved portion is a shrink flange, and the flange portion formed at the second curved portion is an extended flange. Among them, the stamping die has: an upper die; a lower backing plate that cooperates with the upper die to form flange portions at the top plate portion, the longitudinal wall portion, the lower edge of the portion with a deeper wall depth in the longitudinal wall portion, and the first curved portion, and forms a torsional shape portion at the inclined side portion; and a lower die that is arranged adjacent to the lower backing plate and cooperates with the upper die to form the torsional shape portion into a flange portion and forms flange portions at the second curved portion and the recessed side portion that are continuous with the inclined side portion. The upper die has: a top plate forming portion that forms the top plate portion; a side wall forming portion that forms the longitudinal wall portion; a lower edge flange forming portion that forms a flange portion at the edge portion on the opposite side of the top plate portion in the longitudinal wall portion, that is, the lower edge; a first curved portion flange forming portion that forms a flange portion at the first curved portion; an inclined side portion flange forming portion that forms a flange portion at the inclined side portion; a second curved portion flange forming portion that forms a flange portion at the second curved portion; and a recessed side portion flange forming portion that forms a flange portion at the recessed side portion. The lower backing plate has a lower backing plate top plate forming portion, a lower backing plate longitudinal wall forming portion, a lower backing plate lower edge flange forming portion, and a lower backing plate first curved portion flange forming portion. The lower die has: an inclined side forming portion that forms a flange portion at the inclined side portion; a lower die second curved portion flange forming portion that forms a flange portion at the second curved portion;And a flange forming portion at the concave edge portion of the lower die. At the concave edge portion, a flange portion is formed. In the initial stage of forming, a flange portion is formed on the top plate portion, the vertical wall portion, the lower edge of the portion with a deeper wall depth in the vertical wall portion, and the first bending portion by the upper die and the lower backing plate, and a torsional shape portion is formed on the inclined edge portion. In the later stage of forming, the torsional shape portion is formed into a flange portion by the upper die and the lower die, and a flange portion is formed on the second bending portion and the concave edge portion, enabling the formation of the target shape.;

[0008] The stamping forming method according to the present invention uses the stamping forming die of the present invention to form a stamping formed part, which has: a top plate portion; a vertical wall portion, which is continuous from the top plate portion and has a concave portion that depresses from the edge portion on the opposite side of the top plate portion in side view, that is, the lower edge, toward the top plate portion side; and a flange portion, which is formed outward at the lower edge of the vertical wall portion. The concave portion sequentially has, starting from the lower edge of the portion with a deeper wall depth: a first bending portion, which is continuous with the lower edge; an inclined edge portion, which is continuous with the first bending portion; a second bending portion, which is continuous with the inclined edge portion; and a concave edge portion with a shallow wall depth. The flange portion formed on the first bending portion is a shrink flange, and the flange portion formed on the second bending portion is an expansion flange. Among them, the stamping forming method includes: an initial forming process, in which a flange portion is formed on the top plate portion, the vertical wall portion, the lower edge of the portion with a deeper wall depth in the vertical wall portion, and the first bending portion by the upper die and the lower backing plate, and a torsional shape portion is formed on the inclined edge portion; and a later forming process, in which, in a state where the blank is clamped by the upper die and the lower backing plate, the lower die is relatively moved with respect to the upper die to form the torsional shape portion into a flange portion, and a flange portion is formed on the second bending portion and the concave edge portion, and the target shape is formed.

[0009] According to the stamping forming die and the stamping forming method of the present invention, in the initial stage of forming, a flange portion is formed on the top plate portion, the vertical wall portion, the lower edge of the portion with a deeper wall depth in the vertical wall portion, and the first bending portion by the upper die and the lower backing plate, and a torsional shape portion is formed on the inclined edge portion. In the later stage of forming, the torsional shape portion is formed into a flange portion by the upper die and the lower die, and a flange portion is formed on the second bending portion and the concave edge portion, enabling the formation of the target shape. Therefore, it can also be applied to stamping formed parts with wrinkles and cracks generated on the flange itself, and can simultaneously suppress the wrinkles and cracks generated on the flange. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is an explanatory drawing (part 1) of the stamping forming die according to the embodiment of the present invention.

[0011] Figure 2It is an explanatory diagram (part 2) of the stamping die related to the embodiment of the present invention.

[0012] Figure 3 They are explanatory diagrams respectively showing the stamping die related to the embodiment of the present invention. Figure 3 In (a), the upper die is shown. Figure 3 In (b), the lower backing plate is shown. Figure 3 In (c), the lower die is shown.

[0013] Figure 4 It is an explanatory diagram of the stamping method related to the embodiment of the present invention.

[0014] Figure 5 It is an explanatory diagram of the state of the die in the pre-forming process of the stamping method related to the embodiment of the present invention.

[0015] Figure 6 It is an explanatory diagram of the state of the die in the initial forming process of the stamping method related to the embodiment of the present invention.

[0016] Figure 7 It is Figure 4 An enlarged view of the AA part in the formed part in the initial forming process.

[0017] Figure 8 It is an explanatory diagram for explaining the mechanism of suppressing the generation of wrinkles in the initial forming process.

[0018] Figure 9 It is an explanatory diagram of the state of the die in the later forming process of the stamping method related to the embodiment of the present invention.

[0019] Figure 10 It is Figure 4 An enlarged view of the BB part in the target shape in the later forming process.

[0020] Figure 11 It is an explanatory diagram for explaining the mechanism of suppressing the generation of cracks in the later forming process.

[0021] Figure 12 It is an explanatory diagram for explaining the target shape in the embodiment and the problems generated in the forming process of the target shape.

[0022] Figure 13 It is for explaining Figure 12 The mechanism of generating wrinkles and cracks in the forming process of the target shape shown.

[0023] Figure 14 It is showing Figure 4 Another example of the intermediate formed part. Detailed Description of the Invention

[0024] Before describing the stamping die and the stamping method according to the present embodiment, an example of a stamped part to be formed by the present invention will be described in terms of its shape and problems based on Figure 12 , Figure 13 to explain its shape and problems. Figure 12 The stamped part 1 shown is a floor front cross member as an automotive part. The stamped part 1 has: a top plate portion 3; a longitudinal wall portion 5 that is continuous from the top plate portion 3 and has a concave portion 7 that is recessed from the edge portion on the opposite side of the top plate portion in a side view, that is, the lower end edge 11, toward the top plate portion 3; and a flange portion 9 that is formed outward at the lower end edge 11 of the longitudinal wall portion 5.

[0025] Moreover, the concave portion 7 has: a pair of inclined edge portions 13 that are continuous from the lower end edge 11 of the portion with a deeper wall depth; and a concave edge portion 15 of the portion with a shallower wall depth that connects the ends of the inclined edge portions 13. A pair of first bending portions 17 that bend from the lower end edge 11 of the portion with a deeper wall depth to the inclined edge portions 13 and a pair of second bending portions 19 that bend from the inclined edge portions 13 to the portion with a shallower wall depth are formed. The flange portion 9 formed at the first bending portion 17 is a shrink flange deformation, and the flange portion 9 formed at the second bending portion 19 is an expand flange deformation.

[0026] In the case where such a stamped part 1 is formed by an existing stamping method, in the portion that becomes a shrink flange deformation (portion a surrounded by a circular dotted line in the figure), wrinkles are likely to occur due to excess metal, and in the portion that becomes an expand flange deformation (portion b surrounded by a circular dotted line in the figure), cracks are likely to occur due to insufficient material.

[0027] Based on Figure 13 to explain the mechanism of generation of such wrinkles and cracks. Figure 13 is a diagram for explaining the material flow in the forming process in the EE portion surrounded by a dotted line in Figure 12 , showing a top view observation ( Figure 13 (a) of Figure 13 ) and a side view observation ( Figure 12 (b) of Figure 13In the figure, the dashed line is the front end of the blank before forming, and the solid line is the edge of the flange portion 9 formed into the target shape. In addition, points D and B in the figure are the points corresponding to the R end points of the first bending portion 17 in the blank before forming, and correspondingly, in the side view, the intersection points of the lines perpendicular to the edge of the target shape from points D and B with the edge of the target shape are points D' and B'. Similarly, points A and E in the figure are the points corresponding to the R end points of the second bending portion 19 in the blank before forming, and correspondingly, in the side view, the intersection points of the lines perpendicular to the edge of the target shape from points E and A with the edge of the target shape are points A' and E'. As Figure 13 shown in the side view of (b), the material flows substantially perpendicular to the ridge line (curved line). Therefore, in portion a, it flows in the direction approaching the material, and in portion b, it flows in the direction away from the material. Thus, wrinkles are likely to occur in portion a, and cracks are likely to occur in portion b.

[0028] To solve such problems, the inventor came up with a stamping die and a stamping method that can avoid the concentration of compressive strain and tensile strain in each part by interposing a preformed part 20 that can easily make the material flow from the part where the shrink flange deformation occurs to the part where the stretch flange deformation occurs during the forming process. Specifically, the stamping die and the stamping method are composed of the following structures.

[0029] The stamping die 21 according to the present embodiment is, for example, a stamping die for forming Figure 12 the stamping part 1 as shown. Figure 12 The stamping part 1 shown has: a top plate portion 3; a longitudinal wall portion 5 that is continuous from the top plate portion 3 and has a concave portion 7 that is recessed from the edge portion on the opposite side of the top plate portion in the side view, that is, the lower end edge 11, toward the top plate portion 3; and a flange portion 9 that is formed outward at the lower end edge 11 of the longitudinal wall portion 5. In addition, the concave portion 7 successively has from the lower end edge 11 of the portion with a deep wall depth: a first bending portion 17 that is continuous with the lower end edge 11; an inclined edge portion 13 that is continuous with the first bending portion 17; a second bending portion 19 that is continuous with the inclined edge portion 13; and a concave edge portion 15 with a shallow wall depth. Moreover, the flange portion 9 formed at the first bending portion 17 is a shrink flange, and the flange portion 9 formed at the second bending portion 19 is a stretch flange. As Figure 1 , Figure 2As shown, the stamping die 21 includes an upper die 23, a lower backing plate 27, and a lower die 29. The lower backing plate 27 cooperates with the upper die 23 to form a flange portion 9 at the top plate portion 3, the longitudinal wall portions 5, the lower end edge 11 of the portion with a deep wall depth in the longitudinal wall portions 5, and the first bending portion 17, and to form a torsion-shaped portion 25 at the inclined edge portion 13. The lower die 29 is arranged adjacent to the lower backing plate 27 and cooperates with the upper die 23 to form the torsion-shaped portion 25 into the flange portion 9, and to form the flange portion 9 at the second bending portion 19 and the concave edge portion 15 continuous with the inclined edge portion 13. In addition, the upper and lower of the upper die and the lower die are expressions indicating a relative relationship, not necessarily limited to up and down, but expressing a paired relationship.

[0030] As Figure 2 , Figure 3 shown in (a) of FIG., the upper die 23 has a top plate forming portion 23a, a longitudinal wall forming portion 23b, a lower end edge flange forming portion 23c, a first bending portion flange forming portion 23d, an inclined edge portion flange forming portion 23e, a second bending portion flange forming portion 23f, and a concave edge portion flange forming portion 23g. The top plate forming portion 23a forms the top plate portion 3. The longitudinal wall forming portion 23b forms the longitudinal wall portions 5. The lower end edge flange forming portion 23c forms the flange portion 9 at the lower end edge 11 of the longitudinal wall portion 5. The first bending portion flange forming portion 23d forms the flange portion 9 at the first bending portion 17. The inclined edge portion flange forming portion 23e forms the flange portion 9 at the inclined edge portion 13. The second bending portion flange forming portion 23f forms the flange portion 9 at the second bending portion 19. The concave edge portion flange forming portion 23g forms the flange portion 9 at the concave edge portion 15.

[0031] As Figure 1 , Figure 3 shown in (b) of FIG., the lower backing plate 27 has a lower backing plate top plate forming portion 27a, a lower backing plate longitudinal wall forming portion 27b, a lower backing plate lower end edge flange forming portion 27c, and a lower backing plate first bending portion flange forming portion 27d. The lower backing plate top plate forming portion 27a has a shape corresponding to the top plate forming portion 23a of the upper die 23. The lower backing plate longitudinal wall forming portion 27b has a shape corresponding to the longitudinal wall forming portion 23b of the upper die 23. The lower backing plate lower end edge flange forming portion 27c has a shape corresponding to the lower end edge flange forming portion 23c of the upper die 23. The lower backing plate first bending portion flange forming portion 27d has a shape corresponding to the first bending portion flange forming portion 23d of the upper die 23. In the lower backing plate 27, between the lower backing plate first bending portion flange forming portions 27d adjacent in the axial direction, that is, the portion opposed to the second bending portion flange forming portion 23f and the concave edge portion flange forming portion 23g of the upper die 23, becomes a hollow portion 31, and the lower die 29 is arranged in the hollow portion 31.

[0032] As Figure 1 , Figure 3As shown in FIG. (c), the lower die 29 is configured to be movable independently of the lower backing plate 27. The lower die 29 has: a lower die inclined-edge flange forming portion 29a that forms a flange portion 9 on the inclined edge portion 13; a lower die second-bending flange forming portion 29b that forms a flange portion 9 on the second bending portion 19; and a lower die concave-edge flange forming portion 29c that forms a flange portion 9 on the concave edge portion.

[0033] Next, a method for forming the front floor cross member shown as an example in the forming Figure 12 will be described using the stamping die 21 of the present embodiment as described above. As Figure 4 shown, the stamping method of the present embodiment includes a pre-forming start process S1, an initial forming process S3, and a final forming process S5 in which a blank 33 is set in the stamping die 21. Hereinafter, based on Figures 4 to 11 each process will be described in detail. In addition, when describing the movement of the die Figure 5 , Figure 6 , Figure 9 , in order to show the forming state of the blank 33, the upper die 23 is shown as a perspective view.

[0034] <Pre-forming start process> <Q

[0035] In the pre-forming start process S1, as Figure 5 shown, a blank 33 made of a metal plate is placed on the lower backing plate 27. At this time, the lower die 29 is retracted downward, and its upper surface, i.e., the lower die concave-edge flange forming portion 29c, is located below the lower backing plate lower-end-edge flange forming portion 27c of the lower backing plate 27.

[0036] <Initial forming process>

[0037] In the initial forming process S3, as Figure 6 shown, the upper die 23 is moved toward the lower backing plate 27 to the forming bottom dead center. As a result, a flange portion 9 is formed on the top plate portion 3, the longitudinal wall portions 5, the lower end edge 11 of the portion with a deep wall depth in the longitudinal wall portions 5, and the first bending portion 17 by the upper die 23 and the lower backing plate 27, and a torsion-shaped portion 25 ( Figure 7 ) is formed on the inclined edge portion 13. In the state where the upper die 23 is moved to the forming bottom dead center as shown in Figure 6 , there is no lower die 29 sandwiching the blank 33 at the portions corresponding to the inclined-edge flange forming portion 23e, the second-bending flange forming portion 23f, and the concave-edge flange forming portion 23g in the upper die 23 ( Figure 3 ). Therefore, a flange portion 9 is formed on the first bending portion 17 on the lower end side of the inclined edge portion 13 as shown in Figure 7 , but no flange portion 9 is formed on the concave edge portion 15. As a result, the torsion-shaped portion 25 is formed.

[0038] Moreover, as Figure 7 shown, one end side of the torsion-shaped portion 25 is connected to the flange portion 9 formed on the first bent portion 17, and the other end side is connected to the end portion 15a of the blank before forming, thereby forming a twisted shape. When forming the torsion-shaped portion 25, as Figure 7 indicated by the arrow in, material flows from the first bent portion 17 side to the inclined edge portion 13, and the remaining material in the shrink flange deformation is alleviated, and the generation of wrinkles can be suppressed.

[0039] Based on Figure 8 this, the mechanism of the material flow is described. Figure 8 is a diagram for explaining the material flow during the forming process of the CC portion enclosed by a dashed line in Figure 7 , showing the state of the intermediate formed part 20 observed from above and from the side. In addition, in Figure 7 , the thin dashed line is the end edge of the blank 33 before forming, the thick dashed line is the end edge of the intermediate formed part 20, and the solid line is the end edge of the flange portion 9 in the target shape. Points A to E and points A' to E' in the figure are the same points as those Figure 8 shown in. That is, point A in the figure is the R finish of the second bent portion 19 in the blank 33 and is the front end position of the torsion-shaped portion 25. Point B is the point corresponding to the R finish of one of the existing blank portions where shrink flange deformation occurs ( Figure 13 ), and point B' is the intersection of the line perpendicular to the end edge of the torsion-shaped portion 25 from point B in the side view and the end edge of the torsion-shaped portion 25. Point D is the R finish of the first bent portion 17 in the blank 33, and point D' is the intersection of the line perpendicular to the end edge of the target shape from point D in the side view and the end edge of the target shape. Figure 13 ) corresponding point, and point B' is the intersection of the line perpendicular to the end edge of the torsion-shaped portion 25 from point B in the side view and the end edge of the torsion-shaped portion 25. Point D is the R finish of the first bent portion 17 in the blank 33, and point D' is the intersection of the line perpendicular to the end edge of the target shape from point D in the side view and the end edge of the target shape.

[0040] Due to the shrink flange deformation, the distance from point B' to point D' is shorter than the distance from point B to point D (B'D' < BD), and wrinkles are likely to occur in the first bent portion 17 due to the remaining material. On the other hand, if observed three-dimensionally, the distance from point A to point B' is longer than the distance from point A to point B (AB' > AB), so the material is stretched toward point A and flows deviating from Figure 13 the "substantially perpendicular to the ridge line" shown in the a portion of. Therefore, compared with the material flow of the arrow in the existing Figure 13 wrinkle generation region, the material flow shown by the arrow in Figure 8 near point A is generated. Through this material flow, the remaining material in the shrink flange deformation formed in the initial forming stage is alleviated, and the generation of wrinkles can be prevented.

[0041] In addition, in the initial forming process S3, as Figure 14As shown, a bending portion 35 may also be formed at the middle portion in the height direction of the vertical wall portion 5, and the bending portion 35 has an angle such that the lower side of the vertical wall portion 5 opens outward. The reasons for this are as follows. When applying the present invention, if the vertical wall portion 5 is formed into the flange portion 9 while remaining vertical, the bending angle between the vertical wall portion 5 and the flange portion 9 becomes larger due to springback, and warping (curl) is likely to occur in the vertical wall portion 5. By forming the bending portion 35, the flange portion 9 can be formed using a die in a V-shaped with the front end downward, so that the bending angle between the vertical wall portion 5 and the flange portion 9 can be sharpened, and the height of the vertical wall portion 5 adjacent to the flange portion 9 can be reduced to suppress warping. As a result, it is easy to form only a part of the flange portion 9, that is, the shrink flange deformed portion.

[0042] <Post-forming process>

[0043] In the post-forming process S5, in a state where the blank 33 is clamped by the upper die 23 and the lower backing plate 27, as Figure 9 shown, the lower die 29 is moved toward the upper die 23 to form the torsion-shaped portion 25 into the flange portion 9, and the flange portion 9 is formed at the second bending portion 19 and the concave edge portion 15 to form the target shape. During the forming process of the post-forming process S5, as Figure 10 the arrow in shows, by retracting the torsion from the torsion-shaped portion 25 that has absorbed the Figure 7 material allowance, the remaining material is used to cause material inflow into the extended flange deformed portion, so that the material shortage in the extended flange deformed portion is alleviated, and the generation of cracks can be suppressed.

[0044] Based on Figure 11 to explain the mechanism of this material flow. Figure 11 is a diagram for explaining the material flow during the forming process of the DD portion enclosed by a dotted line in Figure 10 , showing the state of top view observation and side view observation Figure 10 . In addition, in Figure 11 , the thin dotted line is the end edge of the blank before forming, the thick dotted line is the end edge of the torsion-shaped portion 25, and the solid line is the end edge of the flange portion 9 in the target shape. In addition, the points A to E and A' to E' in the figure are the same points as those Figure 13 shown.

[0045] Due to the deformation of the stretching flange, the distance from point A' to point E' is longer than the distance from point A to point E (A'E' > AE), and cracks are likely to occur in the second bending portion 19 due to the material shortage caused by the forming of the flange portion 9. On the other hand, when observed three-dimensionally, the distance from point D' to point E' is shorter than the distance from point D' to point E (D'E' < D'E), so the material is pressed toward the A' side and flows deviating from " Figure 13 substantially perpendicular to the ridge line" shown in the b portion of Figure 13 . Therefore, compared with the material flow of the arrow in the crack generation area of the existing Figure 11 , the material flow shown by the arrow near point A' is generated. Through this material flow, the material shortage in the stretching flange deformation formed in the later forming process S5 is alleviated, and the generation of cracks can be prevented.

[0046] As described above, in the case of the stamping die 21 of the present embodiment, the flange portion 9 is formed at the lower end edge 11 and the first bending portion 17 of the portion with a deep wall depth in the vertical wall portion 5 by the upper die 23 and the lower backing plate 27, and the torsion shape portion 25 is formed at the inclined edge portion 13. Moreover, in the later stage of forming, the torsion shape portion 25 can be formed into the flange portion 9 by the upper die 23 and the lower die 29, and the flange portion 9 is formed at the second bending portion 19 and the concave edge portion 15 to form the target shape. Therefore, in the initial stage of forming, by first forming only the portion that becomes the shrink flange deformation, the torsion shape portion 25 that promotes the flow of the material toward the portion that becomes the stretching flange deformation is formed. Moreover, in the later stage of forming, by forming the portion that becomes the stretching flange deformation, the material shortage due to the stretching flange deformation can be suppressed by the material flow from the torsion shape portion 25 to form the target shape.

[0047] In this way, the strain of the dangerous portion where shrink flange wrinkles are generated and the dangerous portion where stretching flange cracks are generated is dispersed. As a result, in the initial forming process S3, the generation of wrinkles caused by the shrink flange deformation is suppressed, and in the later forming process S5, the generation of cracks caused by the stretching flange deformation is suppressed, and the generation of wrinkles and cracks can be suppressed throughout the process.

[0048]

Example

[0049] To confirm the effects of the present invention, Figure 12The front floor cross member component shown was stamped and formed as an example of the target shape. The material is a steel plate with a tensile strength of 1180 MPa-class and a thickness of 1.4 mm. First, as a comparative example, without forming the torsion shape portion 25, the target shape was formed in one process, and stamping was performed by crash forming by using a pad that presses the top plate portion. Next, as an embodiment of the present invention, stamping including the initial forming process S3 and the subsequent forming process S5 was performed using the stamping die 21 described in the embodiment. In the initial forming process S3, flange portions 9 were formed at the lower end edge 11 and the first bending portion 17 of the portion where the wall depth is deep in the longitudinal wall portion 5, and the torsion shape portion 25 was formed at the inclined edge portion 13. In the subsequent forming process S5, the torsion shape portion 25 was formed into a flange portion 9, and flange portions 9 were formed at the second bending portion 19 and the concave edge portion 15 to form the target shape. In addition, any of the forming processes is crash forming by using a pad that presses the top plate portion.

[0050] In the case of the comparative example, wrinkles are generated at the portion a shown in Figure 12 and cracks are generated at the portion b, and the target shape cannot be obtained. On the other hand, in the embodiment of the present invention, neither cracks nor wrinkles are generated in the flange portion 9, and a high-quality stamped part 1 can be obtained. The above shows that the present invention is effective for suppressing stretching flange cracks and shrinkage flange wrinkles during the forming of a stamped part having a flange portion and a large variation in the longitudinal wall depth.

[0051] Industrial applicability

[0052] According to the present invention, it is possible to provide a stamping die and a stamping method that can also be applied to a stamped part in which wrinkles and cracks are generated in the flange itself and can simultaneously suppress the wrinkles and cracks generated in the flange.

[0053] Explanation of reference numerals

[0054] 1... Stamped forming part; 3... Top plate part; 5... Longitudinal wall part; 7... Concave part; 9... Flange part; 11... Lower edge of the deeper part; 13... Inclined edge part; 15... Concave edge part; 15a... Blank end; 17... First bending part; 19... Second bending part; 20... Intermediate forming part; 21... Stamped forming die; 23... Upper die; 23a... Top plate forming part; 23b... Longitudinal wall forming part; 23c... Lower edge flange forming part; 23d... First bending part flange forming part; 23e... Inclined edge part flange forming part; 23f... Second bending part flange forming part; 23g... Concave edge part flange forming part; 25... Twisted shape part; 27... Lower backing plate; 27a... Lower backing plate top plate forming part; 27b... Lower backing plate longitudinal wall forming part; 27c... Lower backing plate lower edge flange forming part; 27d... Lower backing plate first bending part flange forming part; 29... Lower die; 29a... Lower die inclined edge part flange forming part; 29b... Lower die second bending part flange forming part; 29c... Lower die concave edge part flange forming part; 31... Hollow part; 33... Blank; 35... Bending part.

Claims

1. A stamping die for forming a stamped part, the stamped part having: a top plate portion; a longitudinal wall portion that is continuous with the top plate portion and has a recess that is recessed from the edge portion on the opposite side of the top plate portion in side view, i.e., the lower edge, toward the top plate portion; and a flange portion that is formed outwardly at the lower edge of the longitudinal wall portion. The recess successively has from the lower edge of the portion with a deeper wall depth: a first bending portion that is continuous with the lower edge; an inclined edge portion that is continuous with the first bending portion; a second bending portion that is continuous with the inclined edge portion; and a recessed edge portion with a shallower wall depth. The flange portion formed at the first bending portion is a shrinking flange, and the flange portion formed at the second bending portion is an expanding flange. The stamping die is characterized by having: an upper die; a lower backing plate that cooperates with the upper die to form flange portions at the top plate portion, the longitudinal wall portion, the lower edge of the portion with a deeper wall depth in the longitudinal wall portion, and the first bending portion, and to form a twisted shape portion at the inclined edge portion; and a lower die that is arranged adjacent to the lower backing plate and cooperates with the upper die to form the twisted shape portion into a flange portion and to form flange portions at the second bending portion that is continuous with the inclined edge portion and the recessed edge portion. The upper die has: a top plate forming portion that forms the top plate portion; a longitudinal wall forming portion that forms the longitudinal wall portion; a lower edge flange forming portion that forms a flange portion at the edge portion on the opposite side of the top plate portion in the longitudinal wall portion, i.e., the lower edge; a first bending portion flange forming portion that forms a flange portion at the first bending portion; an inclined edge portion flange forming portion that forms a flange portion at the inclined edge portion; a second bending portion flange forming portion that forms a flange portion at the second bending portion; and a recessed edge portion flange forming portion that forms a flange portion at the recessed edge portion. The lower backing plate has a lower backing plate top plate forming portion, a lower backing plate longitudinal wall forming portion, a lower backing plate lower edge flange forming portion, and a lower backing plate first bending portion flange forming portion. The lower die has: a lower die inclined edge portion flange forming portion that forms a flange portion at the inclined edge portion; a lower die second bending portion flange forming portion that forms a flange portion at the second bending portion; and a lower die recessed edge portion flange forming portion that forms a flange portion at the recessed edge portion. In the initial stage of forming, the upper die and the lower backing plate are used to form flange portions at the top plate portion, the longitudinal wall portion, the lower edge of the portion with a deeper wall depth in the longitudinal wall portion, and the first bending portion, and to form a twisted shape portion at the inclined edge portion. In the later stage of forming, the upper die and the lower die are used to form the twisted shape portion into a flange portion and to form flange portions at the second bending portion and the recessed edge portion, enabling the formation of the target shape.

2. A stamping method using the stamping die according to claim 1 to form a stamped part, the stamped part having: a top plate portion; a longitudinal wall portion that is continuous with the top plate portion and has a recess that is recessed from the edge portion on the opposite side of the top plate portion in side view, i.e., the lower edge, toward the top plate portion; and a flange portion that is formed outwardly at the lower edge of the longitudinal wall portion. The recess has, in order from the lower end edge of the portion with a greater wall depth: a first bent portion continuous with the lower end edge; an inclined edge portion continuous with the first bent portion; a second bent portion continuous with the inclined edge portion; and a recessed edge portion with a shallower wall depth. The flange portion formed at the first bent portion is a shrink flange, and the flange portion formed at the second bent portion is an extension flange. The stamping method is characterized by comprising: An initial forming process, in which a flange portion is formed at the top plate portion, the longitudinal wall portion, the lower end edge of the portion with a greater wall depth in the longitudinal wall portion, and the first bent portion by the upper die and the lower backing plate, and a torsion-shaped portion is formed at the inclined edge portion; and A final forming process, in which, with the blank clamped between the upper die and the lower backing plate, the lower die is relatively moved with respect to the upper die to form the torsion-shaped portion into a flange portion, and flange portions are formed at the second bent portion and the recessed edge portion to form a target shape.

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